Near-term prediction of impact-relevant extreme temperature indices

A previous study of predictability of European temperature indices, with the Met Office Hadley Centre Decadal Prediction System (DePreSys) has revealed significant skill in predictions of 5/10-year average indices of summer mean and maximum 5-day average temperatures based on daily maximum and minimum temperatures for a large area of Europe, particularly in the Mediterranean. This study extends this work to indices relevant to high heat-related impacts on human health and maize yields in Europe,for use in future adaptation to increasingly frequent heatwave events. The DePreSys System to used to make decadal predictions of the number of days above critical thresholds for daily maximum and daily minimum Summer temperatures and the skill of these predictions are assessed compared to a preceeding observed climatology and persistence. We find skill beyond observed climatology and persistence for the indices studied for parts of Europe. Areas in the Mediterranean provide the most skillful decadal predictions and they are less skillful in Northern/Central Europe. By comparison to a parallel system, which is not initialised with observations, we find this skill is not due to initialisation but to the model forcing recreating the trend in these indices. The UK is also considered but it is determined this system is not appropriate for predicting these indices in the UK as they are not skillful beyond observed climatology.